The invention concerns a method of operating a stationary electrical power plant connected to a power supply network. Upon the occurrence of a dynamic network fault in the power supply network, in particular an electric short-circuit, at least one fault value is ascertained depending on a state value of at least one operating parameter of the power plant.
Dynamic network faults, in particular electric short-circuits, in power supply networks (e.g. in the public grid) can cause high loads to components connected to the network. Dynamic network (grid) faults are voltage dips or voltage fluctuations in a duration range of a few hundred milliseconds (ms) up to for instance 700 ms, in particular below 500 ms. Parallel mode means that the grid dictates the nominal voltage and nominal frequency, as well as the phase of the AC voltage of the AC generator. Particularly in the case of a power plant connected to a power supply network, short-circuits cause high current strengths in the stator windings, connected to the power supply network, of an electric generator of the power plant, which as a further consequence can also result in high current flows in the rotor windings of the generator. In addition, high short-circuit currents cause an increase in the torque acting on the generator shaft connected to the rotor. The generator shaft is generally connected to the shaft of an internal combustion engine by a coupling device whereby a torque produced in that way can be transmitted to the internal combustion engine by way of the coupling device and can bring about unwanted vibration and oscillations in the internal combustion engine.
In order to counteract such network faults and to promote the stability of a power plant during and after the network fault, a regulating device for the internal combustion engine, can make suitable counter-measures. Thus, the synchronicity of the generator with the power supply network is maintained by the mechanical power of the internal combustion engine connected to the generator being suitably adapted to the electric power which can be delivered by the generator to the power supply network. That can be effected, for example, by adaptations in respect of the combustion process, like for example a delay in or interruption of ignition or a change in position of corresponding actuators of the internal combustion engine (for example butterfly valve or fuel metering valve).
To prevent damage to the power plant as a result of network faults, in particular electric short-circuits, or to minimize same, maintenance plans usually specify that maintenance is effected after a certain number of short-circuits occurring. In that respect, however, no distinction is drawn as to whether the network fault or short-circuit which has occurred is a serious network fault or only a minor network fault. The reaction of the power plant or its components (for example generator, coupling, internal combustion engine) to the network fault is also not taken into consideration in previously known maintenance plans. As a result, a maintenance plan can provide for maintenance of the power plant immediately after a fault although the fault which has occurred was only a minor network fault which had scarcely any effects on the power plant. On the other hand, a maintenance plan can provide for maintenance of the power plant only after a number of electric short-circuits have occurred, in which respect the first network fault which has occurred already had a high damage potential. In addition, known maintenance plans also fail to provide information about the components of the power plant to be investigated, in the next maintenance operation.